Process for producing exogenous protein in the milk of transgenic mammals and a process for purifying proteins therefrom

ABSTRACT

The invention relates to a method of producing a protein of interest, comprising making a non-human transgenic mammal that produces said protein in its milk, obtaining said milk from the non-human transgenic mammal and purifying said protein of interest from the milk. Transgenic bovine animals were generated, which are able to produce human growth hormone in mammary glands. The method involves cloning of a genetic construct encoding hGH gene and beta casein promoter conveniently in an expression vector. It also includes transfection procedures into fetal bovine somatic cells, generally fibroblasts, and the nuclear transfer into enucleated bovine oocytes, generating thus transgenic embryos. The method also includes other procedures to generate transgenic embryos for the further expansion of the transgenic herd, such as the subcloning of transgenic female bovines, the superovulation of transgenic cows and their insemination with semen from a non-transgenic or a transgenic male bovine, and the superovulation of non-transgenic cows and their insemination with semen from a transgenic male bovine. Afterwards, transgenic embryos give rise to transgenic cattle that produce human growth hormone in huge amounts in their milk, from which the hormone is completely purified and analysed to fulfill all the requirements for the manufacture of a pure biopharmaceutical product.

This application claims the benefit of priority to U.S. ProvisionalApplication Ser. No. 60/556,026, filed Mar. 25, 2004; U.S. ProvisionalApplication Ser. No. 60/556,027, filed Mar. 25, 2004; U.S. ProvisionalApplication Ser. No. 60/506,735, filed Sep. 30, 2003; and U.S.Provisional Application Ser. No. 60/506,736, filed Sep. 30, 2003, whichapplications are hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

Protein factors and hormones involved in human health care have beencurrently produced by pharmaceutical industry by extraction or byrecombinant technology in the last decades. Expression of geneticconstructs involving the desired genes were successfully expressed inbacteria, yeast or mammalian cell lines. However, the use of mammaliancell cultures to obtain complex proteins, such as those which require aproper glycosylation pattern, involves high cost procedures.

Recombinant DNA technology has been used increasingly over the pastdecade for the production of commercially important biologicalmaterials. To this end, the DNA sequences encoding a variety ofmedically important human proteins have been cloned. These includeinsulin, plasminogen activator, alpha1-antitrypsin and coagulationfactors VIII and IX. At present, even with the emergent recombinant DNAtechniques, these proteins are usually purified from blood and tissue,an expensive and time consuming process which may carry the risk oftransmitting infectious agents such as those causing AIDS and hepatitis.

Although the expression of DNA sequences in bacteria to produce thedesired medically important protein looks an attractive proposition, inpractice the bacteria often prove unsatisfactory as hosts because in thebacterial cell foreign proteins are unstable and are not processedcorrectly.

Recognizing this problem, the expression of cloned genes in mammaliantissue culture has been attempted and has in some instances proved aviable strategy. However, batch fermentation of animal cells is anexpensive and technically demanding process.

There is therefore a need for a high yield, low cost process for theproduction of biological substances such as correctly modifiedeukaryotic polypeptides. The absence of agents that are infectious tohumans would be an advantage in such a process.

The possibility of obtaining transgenic animals, like cattle, for adesired gene, with the aim of getting large amounts of a human proteinin milk, has been of great interest to the industry. Several groups inthe literature report their success on producing human serum albumin,alpha anti-trypsin, and some other examples in transgenic cows or goats.

Many experiments have been previously performed in mice or rats, andtransgene expression was always preferred to be confined to the mammaryglands since beta casein or lactalbumin promoters were employed, whichrespond only to mammary gland transcription factors in lactatingfemales.

The expression of a heterologous protein exclusively in milk is meant toavoid undesired influence on the host animal health and provide an easymethod for purification.

People are now devoted to set up several systems to improve the yield ofcell transfection or selection, and choose the source of homologousfetal somatic cell to improve survival and immunity conditions of clonedanimals.

On the other hand, there is enormous interest in somatic cell nucleartransfer, mainly to make possible the propagation of elite domesticanimals and engineering of transgenic animals, for agricultural andbiomedical purposes. Briefly, nuclear transfer (NT) involves theenucleation of a recipient oocyte, followed by the transfer of donorcell to the perivitelline space in close apposition of the recipientcytoplast, and their fusion. Development is induced artificially bychemical or physical activation. Production of cloned offspring bysomatic cell nuclear transfer has been successfully attained in sheep(Campbell, K. H., et al., Nature 380:64-66 (1996), 1996; Wells, D. N.,et al., Biol Reprod 57:385-393 (1997); Wilmut, I., et al, Nature385:810-813 (1997)); goat (Baguisi, A., et al., Nat Biotechnol17:456-461 (1999)) and in cow (Cibelli, J. B., et al., Science280:1256-1258 (1998); Kato, Y., et al., Science 282:2095-2098 (1998);Wells, D. N., et al., Reprod Fertil Dev 10:369-378 (1998)).

There are several factors that influence the results of NT including themethods of enucleation, fusion, activation and donor-recipient cellcycle synchrony. High efficiencies in enucleation of recipient oocyteshave been achieved using DNA specific vital dyes to visualize chromatin(Stice, S. L., and Keefer, C. L., Biol Reprod 48:715-719 (1993);Westhusin, M. E., et al., J Reprod Fertil 95:475-480 (1992)). Fusion ofthe donor cell with the recipient oocyte depends on the accuracy of cellalignment in the pulse field, contact of the donor cell with therecipient oocyte and size of the donor cells (Collas, P., et al., AnalBiochem 208:1-9 (1993)). Activation of NT reconstructed embryo has beenrefined and rates of development to blastocysts are equivalent to invitro fertilized oocytes (Liu, L., et al., Mol Reprod Dev 49:298-307(1998)).

Successful development of NT embryos has been accomplished using matureoocytes (Willadsen, S. M., Nature 320:63-65 (1986)), zygotes (McGrath,J., and Solter, D., Dev Biol NY 4:37-55 (1985)), and cleavage-stageembryos (Tsunoda, Y., et al., J Reprod Fertil 96:275-281 (1992)) asrecipient cytoplasts; however, this is dependent on the source of thedonor nucleus. Compatibility of the cell cycle between the recipientcytoplasts and the donor cells is one of the important factors thatinfluence the development of NT embryos. Appropriate synchronization isnecessary to preserve the ploidy of the reconstituted embryo.

The mitotic cell cycle has the following consecutive phases:pre-replication gap (G₁), synthesis of DNA (S), pre-mitotic gap (G₂) andmitosis (M). During a single cell cycle, all genomic DNA replicates onceprior to mitosis. An interphase donor nucleus transferred into anenucleate mature oocyte (metaphase II) undergoes several morphologicalchanges. After fusion, but prior to donor nuclear envelope breakdown(NEBD), the chromosome condenses (PCC). These changes are induced by theactivity of maturation/mitosis/meiosis-promoting factor (MPF) andmitogen-activated protein kinase (MAPK) (Collas, P., and Robl, J. M.,Biol Reprod 45:455-465 (1991)). MPF and MAPK activities are found in allmeiotic and mitotic cells and are highest at metaphase and in mammalianoocytes these high levels also induce arrest in metaphase II. Reductionof MPF and MAPK by fertilization or activation with calcium ionophore isthe signal for completion of meiosis, second polar body emission, spermnucleus decondensation and pronuclear formation.

The direct effect of NEBD and PCC on donor chromatin is dependent on thecell cycle of the donor nucleus at the time of the transfer. DiploidG₀/G₁ nuclei condense to form single chromatids, but tetraploid G₂nuclei condense to form double chromatids. However, nuclei in S phase atthe time of the transfer show a characteristic “pulverized” appearance;PCC produces extensive DNA damage. Therefore, correct ploidy can beproduced by transferring a G₁ or G₀ nuclei into metaphase II oocytes atthe time of activation or before. A second method is to transfer nucleiin previously activated oocyte, in S phase, in this case is possible touse a donor cell in G₁ G₀ or S phase. Because MPF and MAPK are low; thechromatin decondenses, and undergoes DNA replication without PCC andNEBD.

A third synchronization scheme has been reported in mice, wheredevelopment of a live offspring was produced by embryo reconstructionusing a G₂ or metaphase donor cell and an enucleated metaphase 2 oocyte(Cheong, H. T., et al., Biol Reprod 48:958-963 (1993); Kwon, O. Y., andKono, T., Proc Natl Acad Sci USA 93:13010-13013 (1996)). The extrusionof a polar body from the NT reconstructed embryo was reported, resultingin single diploid embryo and a diploid polar body (Kwon, O. Y., andKono, T., Proc Natl Acad Sci USA 93:13010-13013 (1996)). However, thereis no report of polar body formation after NT into enucleated MIIoocytes in cattle, sheep or pigs, suggesting differences between speciesin the mechanics controlling formation of intact spindles and extrusionof polar bodies.

The cell cycle stages of the donor cell and the recipient have beensuggested to be also important to reprogram the donor cell nuclei.Increasing the time between donor nuclei transfer and zygotictranscription may improve nucleus reprogramming. For this reason,several authors activated the oocyte several hours after fusion(Cibelli, J. B., et al., Science 280:1256-1258 (1998);

Wakayama, T., et al., Nature 394:369-374 (1998); Wells, D. N., et al.,Biol Reprod 60:996-1005 (1999)). Other reports applied sequentialnuclear transfer (Stice, S. L., and Keefer, C. L., Biol Reprod48:715-719 (1993)).

An unexplored procedure to increase the time of donor nucleusreprogramming is by nuclear transfer before metaphase II. After germinalvesicle breakdown (GVBD), all the nuclei events are regulated by asubstantial increase in oocyte cytosolic MPF and MAPK, which preventreconstruction of the nuclear envelope and entrance in the S phase untilfertilization or activation. Therefore, a maturing oocyte may be auniversal recipient for metaphase or G₂ donor cell. Even G₁ or G₀ can beused as donor cells if activation induces an S phase before celldivision.

When blastomeres in G₂ or M are used as donor cells, nuclearreprogramming is possible (Cheong, H. T., et al., Biol Reprod 48:958-963(1993); Kwon, O. Y., and Kono, T., Proc Natl Acad Sci USA 93:13010-13013(1996); Liu, L., et al., Mol Reprod Dev 47:255-264 (1997)). Oneexplanation is that some factors are displaced from the chromatin as aresult of chromosome condensation. In fact, for nuclear transfer, NEBDand PCC have been considered morphological signs of nucleusreprogramming. Additionally, at the time of fertilization spermchromatin is extremely condensed, and its volume is considerably smallerthan that of nuclei of somatic cells, and oocyte has the ability toremove sperm nuclear protein. Oocyte chromosomes, during sperm-oocytefusion, are also condensed. It is possible that condensed chromatinconformation may have some biological relevance. Consequently, bymimicking this situation by metaphase nuclear transfer, ametaphase-enucleated recipient could improve NT result. However, fewresearchers have used this approach in domestic animals and usingblastomeres as donor cells (Liu, L., et al., Mol Reprod Dev 47:255-264(1997)).

One goal of this invention is to characterize and refine existingsomatic cell nuclear transfer to a reliable and economical technique toproduce genetically identical calves from adult donor cells.

SUMMARY OF THE INVENTION

The invention relates to a non-human transgenic mammal characterized bythe production of unexpectedly high levels of a recombinant growthhormone in its milk. The recombinant growth hormone may be, but is notlimited to, human growth hormone. The non-human transgenic mammal maybe, but is not limited to, an animal of bovine species.

The invention further relates to a plasmid that provides the expressionof a protein of interest in the mammary cells of mammals in which theexpression is regulated by the beta casein promoter. The protein ofinterest may be, but is not limited to, human growth hormone.

The invention also relates to different methods of making a non-humantransgenic mammal that produce a recombinant growth hormone in its milk.The recombinant growth hormone may be, but is not limited to, humangrowth hormone. The non-human transgenic mammal may be, but is notlimited to, an animal of bovine species.

The invention also relates to a method of producing a protein ofinterest, comprising making a non-human transgenic mammal that producessaid protein in its milk, obtaining said milk from the non-humantransgenic mammal and purifying said protein of interest from the milk.The protein of interest may be, but is not limited to, human growthhormone. The non-human transgenic mammal may be, but is not limited to,an animal of bovine species.

The invention also relates to a method of producing and purifying arecombinant growth hormone from the milk of a transgenic mammal. Therecombinant growth hormone may be, but is not limited to, human growthhormone. The transgenic mammal may be, but is not limited to, an animalof bovine species.

BRIEF DESCRIPTION OF THE FIGS.

FIGS. 1A-1B show the daily milk volume collected from a transgenic cowobtained by the fusion of an enucleated oocyte and a fibroblastpreviously transfected with a plasmid containing the gene which encodesthe human growth hormone (hGH) and a promoter that directs itsexpression to mammary cells.

FIGS. 2A-2C show the bacteria count found in the milk collected from thesame transgenic cow.

FIGS. 3A-3B show the biological activity of the hGH contained in themilk of the same transgenic cow.

FIG. 4A shows the daily mass of hGH produced in the milk of the sametransgenic cow. This magnitude and the daily milk volume collected fromthe transgenic cow are plotted together in FIG. 4B.

FIG. 5A shows the concentration of hGH and insulin-like growth factor-1(IGF-1) in the serum of the same transgenic cow, and the daily mass ofhGH produced in the milk of the same transgenic cow. The concentrationof hGH in the transgenic cow's serum and the daily mass of hGH producedin the milk of the transgenic cow are plotted together in FIG. 5B. InFIG. 5C, the time profiles of the transgenic cow's serum concentrationsof hGH and IGF-1 are plotted together.

FIGS. 6A and 6B show the serum concentration of hGH and insulin-likegrowth factor-1 (IGF-1) in two transgenic calves obtained by subcloningof a cow which is transgenic for the production of hGH in its milk. InFIGS. 6C and 6D, the time profiles of serum concentrations of hGH andIGF-1 are plotted together for each of these transgenic calves.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a non-human transgenic mammal characterized bythe production of unexpectedly high levels of a recombinant growthhormone in its milk. This mammal may be, but is not limited to, ananimal of bovine species. Other species of transgenic mammals may be,but are not limited to, porcine species, ovine species, caprine species,or rodent species.

The recombinant growth hormone can be, but is not limited to, humangrowth hormone. This molecule, also known as somatotropin, is a proteinconsisting in 191 amino acids, with a molecular weight of about 22 kD.It is essential for linear growth and its applications are wellestablished.

The invention also relates to a transgenic mammal, characterized by thefact that the recombinant growth hormone produced in its milkself-stimulates the animal's mammary glands in order to produce moremilk containing said hormone.

The invention also relates to a plasmid comprising a gene encoding aprotein of interest operably linked to a beta casein promoter and a βlactamase gene. This protein of interest can be, but is not limited to,human growth hormone. This plasmid can be pRβhGH.

In a further embodiment, the plasmid additionally includes a neomycinresistance gene for selection of geneticin resistant cells. An exampleof such plasmid is pRNeo.

In a further embodiment, the plasmid includes the gene coding for agreen fluorescent protein such as GFP, which is under control of thecytomegalovirus (CMV) promoter. An example of such a plasmid ispRNeoGreen.

The invention further relates to a plasmid such us those describedabove, which has been linearized by restriction digestion. Inparticular, use of restriction enzime ApaLI is employed and the βlactamase gene is excised.

The deposit procedure under the Budapest Treaty of the plasmidsmencioned above is under way. The name and address of the depository areDSMZ—Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH,Mascheroder Weg 1b, 38124 Braunschweig, Germany. The correspondentaccession numbers will be provided in due course.

The invention further relates to the plasmid constructed on basis of aNeo resistance gene-containing plasmid, into which a modified shorterbeta casein promoter region was inserted upstream a hGH coding region,such as pVEβcashGH. A linear fragment may be obtained from the plasmidpVEβcashGH by excising the beta lactamase gene.

The invention further relates to a method for the transfection ofgenetic constructs using a combination of cationic lipids for liposomeutilization.

Methods of selection of neomycin resistant cells in appropriate mediaare also described, as are methods of selecting green fluorescenttransgenic cells. These cells are picked carefully, so as to avoid celldamage.

The invention also relates to a method of nuclear transfer of cellsarrested in G₀, or at different times of the cell cycle, into enucleatedbovine oocytes.

The invention relates to a method of transgenic embryo transfer intohormone stimulated cow uteri.

According to the invention, a method of determining animal healthparameters is disclosed. Analyses are performed on both the animal'sserum and milk in order to determine such parameters.

The invention further relates to a method of making a non-humantransgenic mammal comprising obtaining a gene which encodes a growthhormone, cloning the gene into a plasmid whereby the gene is operablylinked to a promoter that will direct the expression of the gene inmammary cells, resulting in an expression plasmid, transfecting somaticcells with the expression plasmid so that the plasmid is incorporatedinto the genome of the cells, resulting in transgenic somatic cells,enucleating a mature oocyte, resulting in an enucleated oocyte, fusingone transgenic somatic cell with the enucleated oocyte resulting in amonocell embryo, implanting the embryo in the uterus of a receptivemammal, and monitoring the pregnancy through the birth of the transgenicmammal.

The invention further relates to a method of making a non-humantransgenic mammal comprising extracting somatic cells from a femalemammal which is transgenic for the production of a recombinant growthhormone in its milk, optionally fibroblasts, enucleating a matureoocyte, resulting in an enucleated oocyte, fusing one transgenic somaticcell with the enucleated oocyte resulting in a monocell embryo,implanting the embryo in the uterus of a receptive mammal, andmonitoring the pregnancy through the birth of the transgenic mammal.

The invention further relates to a method of making a non-humantransgenic mammal comprising superovulating a female non-human mammalwhich is transgenic for the production of a recombinant growth hormonein its milk, artificially inseminating the mammal with semen obtainedfrom a male non-human, non-transgenic mammal, to produce embryos,collecting the embryos, implanting the embryos in the uterus of areceptive mammal, and monitoring the pregnancy through the birth of thetransgenic mammal.

The invention further relates to a method of making a non-humantransgenic mammal comprising superovulating a female non-human mammalwhich is transgenic for the production of a recombinant growth hormonein its milk, artificially inseminating the mammal with semen obtainedfrom a male non-human mammal which is transgenic for the production ofsaid recombinant growth hormone, to produce embryos, collecting theembryos, implanting the embryos in the uterus of a receptive mammal, andmonitoring the pregnancy through the birth of the transgenic mammal.

The invention further relates to a method of making a non-humantransgenic mammal comprising superovulating a female non-human,non-transgenic mammal, artificially inseminating the mammal with semenobtained from a male non-human mammal which is transgenic for theproduction of a recombinant growth hormone, to produce embryos,collecting the embryos, implanting the embryos in the uterus of areceptive mammal, and monitoring the pregnancy through the birth of thetransgenic mammal.

The recombinant growth hormone may be, but is not limited to, humangrowth hormone. The non-human transgenic mammal may be, but is notlimited to, an animal of bovine species.

The invention further relates to a method to produce a proteincomprising making a non-human transgenic mammal that produces a proteinof interest in unexpectedly high yields in its milk, obtaining the milkfrom the non-human transgenic mammal, and purifying the protein ofinterest from the milk.

The invention also relates to a method to produce a protein of interestin a non-human transgenic mammal made by a process comprising obtaininga gene which encodes said protein of interest, cloning the gene into aplasmid whereby the gene is operably linked to a promoter that willdirect the expression of the gene in mammary cells, resulting in anexpression plasmid, transfecting somatic cells, optionally fibroblasts,with the plasmid so that the plasmid is incorporated into the genome ofsaid somatic cells, resulting in transgenic somatic cells, enucleating amature oocyte, resulting in an enucleated oocyte, fusing one transgenicsomatic cell with the enucleated oocyte resulting in a monocell embryo,implanting the embryo in the uterus of a receptive mammal, andmonitoring the pregnancy through the birth of the transgenic mammal.

The invention further also relates to a method to produce a protein ofinterest in a non-human transgenic mammal made by a process comprisingextracting somatic cells from a female mammal which is transgenic forthe production of said protein of interest in its milk, optionallyfibroblasts, enucleating a mature oocyte, resulting in an enucleatedoocyte, fusing one transgenic somatic cell with the enucleated oocyteresulting in a monocell embryo, implanting the embryo in the uterus of areceptive mammal, and monitoring the pregnancy through the birth of thetransgenic mammal

The invention also relates to a method to produce a protein of interestin a non-human transgenic mammal made by a process comprisingsuperovulating a female non-human mammal which is transgenic for theproduction of said protein of interest in its milk, artificiallyinseminating the mammal with semen obtained from a male non-human,non-transgenic mammal, to produce embryos, collecting the embryos,implanting the embryos in the uterus of a receptive mammal, andmonitoring the pregnancy through the birth of the transgenic mammal.

The invention also relates to a method to produce a protein of interestin a non-human transgenic mammal made by a process comprisingsuperovulating a female non-human mammal which is transgenic for theproduction of said protein of interest in its milk, artificiallyinseminating the mammal with semen obtained from a male non-human mammalwhich is transgenic for the production of said protein of interest, toproduce embryos, collecting the embryos, implanting the embryos in theuterus of a receptive mammal, and monitoring the pregnancy through thebirth of the transgenic mammal.

The invention also relates to a method to produce a protein of interestin a non-human transgenic mammal made by a process comprisingsuperovulating a female non-human, non-transgenic mammal, artificiallyinseminating the mammal with semen obtained from a male non-human mammalwhich is transgenic for the production of said protein of interest, toproduce embryos, collecting the embryos, implanting the embryos in theuterus of a receptive mammal, and monitoring the pregnancy through thebirth of the transgenic mammal.

The transgenic mammals characterized by the production of unexpectedlyhigh levels of a protein of interest in their milk, can be, but are notlimited to, animals of bovine species. Other species of transgenicmammals may be, but are not limited to, porcine species, ovine species,caprine species or rodent species. The protein of interest can be, butis not limited to, human growth hormone.

The invention further relates to a non-human transgenic mammal of bovinespecies that produces recombinant human growth hormone in its milk,whose genome comprises an integrated plasmid, said plasmid comprisingthe human growth hormone gene and a beta casein promoter that directsexpression of said gene in mammary cells of the mammal.

The invention further relates to a transgenic mammal that produces hGHin unexpectedly high levels, yet does not show the physical growthexpected with such a high level of hGH production. Since transgenicbovines are affected by the presence of human growth hormones, it wouldbe expected that the animals would grow beyond non-transgenic growthrates, and to suffer from conditions such as diabetes mellitus,hypertension, increased risk of cardiovascular disease and enlargementof body organs, including the liver, spleen, kidneys and heart. Suchhigh levels of hGH should render the animal, theoretically, non-viable.However, this is not the case. A mammal, such as a cow, with alarminglyhigh levels of a foreign hormone in its blood, but which is perfectlyhealthy and yields an outstanding productivity of a recombinant proteinconstitutes an unexpected and innovative contribution.

The recombinant human growth hormone of the invention is produced atunexpectedly high levels. The level of human growth hormone produced isgreater than about 1.0 g/L milk. The level of hGH can be greater thanabout 2.0 g/L milk. The level of hGH produced can also be greater thanabout 3.0 g/L milk. In another embodiment, the level of hGH produced canbe greater than about 4.0 g/L milk. In yet another embodiment, the levelof hGH produced can be greater than about 5.0 g/L milk. In a furtherembodiment, the level of hGH produced can be greater than about 6.0 g/Lmilk. In yet a further embodiment, the level of hGH produced is about1.0 g/L milk to about 7.0 g/L milk. In a further embodiment, the levelof hGH produced is about 2.0 g/L milk to about 6.0 g/L milk. In yetanother embodiment, the level of hGH produced is about 2.0 to about 5.0g/L milk.

Additionally, the invention relates to a method of purifying arecombinant growth hormone from the milk of a transgenic mammal, as wellas assays of said hormone. The purification methods can includechromatography and concentration steps. Different types ofchromatography can be employed and include ion exchange chromatography,reverse phase chromatography, molecular exclusion chromatography oraffinity chromatography. The ion exchange chromatography can be anionexchange chromatography. The affinity chromatography can beimmunoaffinity chromatography. Further, multiple chromatography stepsmay be performed.

The invention further relates to a method of purifying a recombinantgrowth hormone from milk of a non-human transgenic mammal that producesa recombinant growth hormone comprising clarifying the milk of anon-human transgenic mammal, resulting in a clarified milk, andsubjecting the clarified milk to chromatography, resulting in purifiedrecombinant growth hormone.

The invention further relates to a method of purifying a recombinantgrowth hormone from milk of a non-human transgenic mammal that producesa recombinant growth hormone comprising clarifying the milk of anon-human transgenic mammal, resulting in a clarified milk, subjectingthe clarified milk to expanded-bed anion exchange chromatography,resulting in an anion exchange chromatographed material, subjecting theanion exchange chromatographed material to reverse phase chromatography,resulting in a reverse phase chromatographed material, subjecting thereverse phase chromatographed material to anion exchange chromatography,resulting in an anion exchange chromatographed material, subjecting theanionic exchange chromatographed material to molecular exclusionchromatography, resulting in a molecular exclusion chromatographedmaterial, concentrating the molecular exclusion chromatographedmaterial, resulting in a concentrated material, and subjecting theconcentrated material to molecular exclusion chromatography, resultingin pure recombinant growth hormone.

The invention also relates to a method of purifying a recombinant growthhormone from milk of a non-human transgenic mammal that produces arecombinant growth hormone comprising clarifying milk obtained from atransgenic mammal, resulting clarified milk, subjecting the clarifiedmilk to immunoaffinity chromatography, resulting in an immunoaffinitychromatographed material, subjecting the immunoaffinity chromatographedmaterial to reverse phase chromatography, resulting in a reverse phasechromatographed material, subjecting the reverse phase chromatographedmaterial to anionic exchange chromatography, resulting in an anionicexchange chromatographed material, subjecting the anionic exchangechromatographed material to molecular exclusion chromatography,resulting in a molecular exclusion chromatographed material, subjectingthe molecular exclusion chromatographed material to concentration,resulting in a concentrated material, and subjecting the concentratedmaterial to molecular exclusion chromatography, resulting in purerecombinant growth hormone.

The recombinant growth hormone of the purification methods describedabove may be, but is not limited to, human growth hormone. Thetransgenic mammal may be, but is not limited to, a mammal of bovinespecies.

The following examples are illustrative, but not limiting, of the methodand compositions of the present invention. Other suitable modificationsand adaptations of the variety of conditions and parameters normallyencountered in enzymatic production of chemicals and proteinpurification procedures which are obvious to those skilled in the artare within the spirit and scope of the invention.

EXAMPLE 1 Construction of Expression Plasmids

We generated a construct bearing a large portion of the bovine betacasein gene promoter, including a short fragment of the 5′ non-codingbeta casein gene region, fused to the coding sequence of the humangrowth hormone gene. The beta casein region employed in differentconstructs was decreased from 3.8 kbp to about 1.3 kbp. The hGH geneencompasses about 2 to 2.2 kbp depending on whether the intrinsic polyAsignal is included.

The expression cassette was accommodated in the polylinker of a usualcloning vector of the pUC or pBS type.

This promoter ensures the tissue specific and developmentally regulatedexpression of genes under its control, like beta casein, and theheterologous hGH in this case.

The most representative plasmid is pRβhGH, which carries the full-lenghtbovine beta casein promoter, fused to the coding sequence of the humangrowth hormone gene.

Other constructs disclosed are mainly derived from the original one, asdepicted, to improve transfected cell selection or DNA integrationefficiency into the bovine cell genome.

In the first period, co-transfection with a geneticin resistancegene-containing plasmid was performed to help selection, but next, otherconstructs were used, bearing NPT gene for neomycin resistance in thesame vector containing the hGH expression cassette. An example of suchplasmid is pRNeo.

Another plasmid for constitutive expression of green fluorescent proteinwas obtained, which includes the CMV promoter, an enhancer of vegetalorigin (alfalfa), and the green fluorescent protein gene from thejellyfish A. victoria. An example of such plasmid is pRNeoGreen.

Besides, another plasmid was generated. This was constructed on basis ofa Neo resistance gene-containing plasmid, into which a modified shorterbeta casein promoter region was inserted upstream a hGH coding region.This plasmid is pVEβcashGH.

Other constructs were generated in which the β lactamase region wasexcised by ApaLI restriction and the linear fragment containing theentire expression cassette was purified after agarose gelelectrophoresis, and gel extraction.

Constructs were analyzed by restriction enzymes and DNA sequencing, andtheir ability to conduct hGH expression was previously tested in amammary gland cell line by fluorescent antibody recognition.

The preparation of the plasmid pVEβcashGH will be described in detail asan example of this part involving genetic constructs.

Preparation of pVE βcashGH

The aim of this construct is to provide the minimal extension of betacasein promoter region to direct specific regulated transcription of thehGH gene fused immediately downstream, along with its polyA signal in ahost organism.

The use of pVEX as the original vector permits the use of neomycinresistance gene regulated by a tk promoter already present in thisplasmid. The early SV40 promoter comprising 554 bp was eliminated byrestriction with StuI and NdeI, and the last site filled in with Klenow,and self-ligation of the resulting vector.

Beta casein short promoter was obtained after PCR amplification of a 1.3kbp fragment from the 3.8 kbp original gene promoter region, by usingthe following oligos as primers: PB1 5′ TCTACTCGAGGATCATCTATCTGTCCCAAAG(SEQ ID NO: 1) and PB2 5′ CTAGGATCCAATGATCTGATTTTGTGG (SEQ ID NO: 2)This fragment encompasses 1230 bp of the canonical promoter plus 49 bpof the first non coding exon of the beta casein gene.

The hGH gene fragment was obtained by PCR techniques on the originalbovine genomic hGH clone using the following oligos as primers: PB45′CTAGGATCCATGGCTACAGGTAAGCGCC (SEQ ID NO: 3) and GHTE 5′ATGCTGTGTCTGGACGTCCT (SEQ ID NO: 4)The beta casein promoter fragment was blunted with Klenow enzyme andinserted into the BamHI filled-in site of pVEX. After selectingrecombinant clones, we chose a certain direction appropriate to use theunique HindIII site located downstream in pVEX to insert the hGH codingregion.

To this aim, the hGH fragment was also blunted and the plasmid HindIIIsite was filled in as well. Clones were selected which contain betacasein promoter and hGH properly fused to express hGH only under thecontrol of this promoter.

The size of this plasmid is about 8.5 kbp.

Transfection of Somatic Cells

The plasmids pRβhGH (along with another plasmid with the geneticinresistance gene), pRNeo, pRNeoGreen, or pVEβcashGH were then used fortransfecting a primary culture of somatic cells, using calcium phosphateor liposome method. Fetal calf fibroblasts were generally employed to betransfected.

The transfected cells were selected adding geneticin to the culture.

After a period of 2 to 8 weeks, the cells that were resistant togeneticin were suitable for being used as donor cells to obtaintransgenic clones. Transfected selected cells were analyzed by PCR tocontain the expression cassette, to ensure the appropriate nucleitransfer to generate transgenic embryos.

EXAMPLE 2 Oocyte Enucleation and Metaphase Nuclear Transfer in MatureEnucleated Oocytes Collection and In vitro Maturation of Bovine Oocytes

Bovine oocytes were aspirated from slaughterhouse ovaries and matured inTCM-199+5% FCS at 39° C. for 24 hs. The maturation medium wasequilibrated with CO₂ for at least 2 hours prior to use. Mature oocyteswere denuded by vortexing for 2 minutes in warm TL-HEPES with 1 mg/mlbovine testis hyaluronidase.

Nuclear Transfer with Cumulus Cells Enucleation

Oocytes were mechanically enucleated using a Narishige hydraulicmicromanipulators and Nikon Diaphot microscopy. Enucleation wasperformed with 20 μm beveled and sharpened pipettes. Oocytes werepreviously stained with 5 μg/ml bisbenzimidine (Hoechst 33342¹) dye for20 minutes. Metaphases were enucleated by visualization of the stainedchromosomes under ultraviolet light. Metaphase chromosomes were assessedafter aspiration inside the pipette. A transgenic somatic cell wastransferred into the perivitelline space and tightly opposed to theenucleated oocyte.¹Sigma Chemical Co., St. Louis, Mo., USA

Fusion

A transgenic somatic cell and an enucleated oocyte were manually alignedin the fusion chamber so that the membranes to be fused were parallel tothe electrodes. This was done using a glass embryo-handling pipette.

Fusion by Electrical Means

Fusion was performed using one electrical pulse of 180 volts/cm for 15μs (BTX Electro Cell Manipulator 200)² and monitored with a BTXOptimizer-Graphic Pulse Analyzer. The chamber for pulsing embryosconsisted of two 0.5 mm stainless steel wire electrodes mounted 0.5 mmapart on glass microscope slide. Presumptive zygotes were monitored forfusion, lysis, and fragmentation.²BTX Inc., San Diego, Calif., USA

Assessment of Developmental Competence

Zygotes were evaluated at 48 hours after fertilization for cleavage andafter 7 to 9 days for development to morulae or blastocysts.

EXAMPLE 3 Cell and Embryo Culture

Different donor cells, culture systems and oocyte recipient treatmentswere tested in an experiment aimed at simplifying procedures andincreasing embryo survival rate in a bovine cloning program. Threeculture systems for reconstructed embryos were used when adultfibroblasts were used as donor cells: TCM-199+5% FCS, Menezo+5% FCS(both with VERO cells as co-culture) and SOF without co-culture but withlower O₂ concentration. SOF medium was also used to culturereconstructed embryos when donor cell were genetically andnon-genetically modified fetal fibroblasts. Finally, when geneticallymodified fetal fibroblasts were used as donor cells, recipient oocyteswere previously treated with roscovitine (R), to suspend meiosis andoptimize recipient usability. Oocytes were aspirated from slaughterhouseovaries and matured in TCM-199+5% FCS at 39° C. for 24 hours. For Rtreated group, oocytes were incubated with 25 μM R in TCM 199+5% FCS for24 hours at 39° C. prior to the maturation. Mature oocytes were denudedby vortexing for 3 minutes in TL HEPES with 1 mg/ml bovine testishyaluronidase. Metaphases were assessed and oocytes were enucleated byvisualization with Hoechst 33342 (5 μg/ml) under UV light (<6 seconds).Adult fibroblasts from an Angus bull and fetal fibroblasts from a 45-dayold Jersey female fetus were used as donor cells. Transfection withconstructs containing neomycin resistance gene was performed usingliposomes. After selection with geneticin for 10-15 days, donor cells atG₀/G1 stages were fused to enucleated oocytes by an electrical pulse.After 3 hours, activation was induced by incubation in TL-HEPES with 5μM ionomycin for 4 min and 2 mM 6-DMAP for 3 hours. The oocytes werethen washed with TL-HEPES and co-cultured in either TCM-199+5% FCS+10g/l albumin or Menezo+2% FCS both VERO cells, or in SOF medium andatmosphere of 5% CO₂+5% O₂+90% N₂. Generally, two blastocysts weretransferred non-surgically per recipient cow, and pregnancies at 30-35days determined by ultrasonography. Cleavage (48 hours), development toblastocysts (days 7 to 9) were recorded and analyzed by Chi-square.Cleavage rates and development to blastocysts were higher when embryoswere cultured in SOF. However, no differences were observed in pregnancyrates due to different culture conditions or source of donor cells.Suspension of meiotic maturation for 24 hours did not compromise thedevelopmental competence of recipient oocytes. Therefore, treatment withroscovitine might be used to increase the availability of oocytes for NTprocedures. See Table 1 below. TABLE 1 implanted Treatment n Cleavage(%) Blastocyst (%) recipient Preg. (%) Adult fibroblast 294 156(53.9)^(a) 22 (7.5)^(a) 13 5 (38.4) TC199 + VERO Adult fibroblast 324236 (72.3)^(bc) 29 (8.9)^(a) 17 5 (29.4) Menezo + VERO Adult fibroblast108 81 (75.0)^(bc) 24 (22.2)^(b) 11 5 (45.4) SOF Fetal fibroblast 197122 (61.9)^(ab) 33 (16.7)^(ab) 16 5 (31.6) SOF Transfected fetal 646 476(73.7)^(bc) 128 (19.8)^(b) 56 25 (44.6) fibroblast SOF Transfected fetal228 191 (83.7)^(c) 51 (22.3)^(b) 30 16 (53.3) fibroblast SOF-R Total1797 1262 (70.2) 287 (15.9) 143 61 (44.5)

Percentages within Columns with different Superscripts are Different(P<0.05)

The implanted cows are allowed to normally pass the pregnancy up to anatural delivery. Eventually a chirurgic approach (Caesarea) could beused for delivery. The newborns are fed with Ig rich colostrum duringthe first 48 hours, and then synthetic, later natural (all of them freeof animal origin compounds) foods are used.

EXAMPLE 4 Tests Performed on Transgenic Calves and the RecombinantProtein Produced

In the current example, we present a full description of the testsperformed on a particular transgenic calf, which was obtained as aresult of the procedure described in Examples 1 to 3, and on therecombinant protein produced by it. Nonetheless, it should remain clearthat the same set of assays is performed on animals that are born as aconsequence of other methods for obtaining transgenic calves, such asthose that will be described in Examples 5 and 6 below.

It was proved by means of PCR reactions performed on DNA purified fromthe calf's white blood cells, using DNA from non-transgenic jerseycalves as the negative control, that bovine beta casein promoter and thehGH encoding gene are included in the transgenic calf cells genome. Theycan be found together as a unique DNA fragment different to thehomologue beta casein gene of the animal.

It was corroborated, by using a Pharnacia automatic sequencer, that theinserted gene sequence corresponds 100% to the hGH encoding gene. Itincludes the introns, secretion signal and terminator. The bovine betacasein promoter that controls that same hGH gene expression in our calfwas sequenced, too. All those elements coincide exactly with theexpected theoretical sequence from the genetic construct used totransform the cells out of which the clones were generated.

Once known the exactitude of the genetic phase of the experiment, wepassed to prove the recombinant protein produced is the expected one andcoincides in every one of its physical and chemical characteristics withthe natural hGH.

For this purpose, we had to obtain milk from the calf, since the betacasein promoter allows the expression of the recombinant protein only inthe mammary glands, when the animal is at its milk producing time.

The transgenic calf was then induced by a hormone treatment to producemilk by the time it completed her tenth month. By that time the calfweighed 240 kg (approximately 530 lbs).

The first phase of said treatment involved the combined administration,by subcutaneous route, of estrogens (estradiol benzoate, Histeren®,Instituto Rosenbusch) and progestagens (medroxyprogesterone acetate,Pronal®, Aton), comprising 5 successive applications of each drug, in adose of 0.1 mg/kg and 0.25 mg/kg, respectively, every 48 hours (i.e., ondays 1, 3, 5, 7 and 9, assuming that the treatment commences on day 1).

The second phase comprised the administration, by subcutaneous route, ofdexamethasone (Decadron, Sidus) and oxytocin (Orasthin®, Hoechst MarionRoussel); a total amount of 20 mg of the former being injected over aperiod comprising days 18 to 20 (a third of said total mass each day),and 3 applications of 50 IU of the latter, on days 21 to 23.

The information above is summarized in Table 2: TABLE 2 Day 1 2 3 4 5 67 8 9 10 ( . . . ) 17 18 19 20 21 22 23 Histeren (mg/kg) 0.10 0.10 0.100.10 0.10 Pronal (mg/kg) 0.25 0.25 0.25 0.25 0.25 Decadron (mg) 6.66*6.66* 6.66* Orasthin (IU) 50 50 50*Approximately a third of the total mass (20 mg) was administered eachday

As expected, the cow commenced producing colostrum the day after thetreatment had finished, and then, progressively, the quality of theproduced fluid turned to milk. The collected fluid was properly storedand thoroughly analyzed.

Several tests, whose results are shown in FIGS. 1-4, were performed onthe colostrum and milk (for simplicity, both colostrum and milk will behereinafter referred to as “milk”, except when a distinction should bemade). First, the volume of the collected milk was measured. The initialmilk productivity (first five lactating days) was approximately 1,650mL/day. During the first productive month, two manual milkings per daywere performed, one in the morning and one in the afternoon (thecontribution of each udder to the final volume can be noticed); whereasfrom the second month forth, as the production of milk started toincrease, three milkings per day were performed (in the morning, atnoon, and in the afternoon). The daily volumes increased in a more orless continuous way, until reaching close to the 10,000 mL three monthsafter the first milking. Detailed information regarding this topic (FIG.1A) can be visualized in the curve of daily milk volume vs. date (FIG.1B).

In parallel with the measurements of milk volume, microbiological assayswere performed on the milk, whose results (FIG. 2A) are shown in thecorresponding plots of CFU (Colony-forming units) per ml vs date and(FIGS. 2B-2C).

Biological activity (of hGH) was also assessed by a biological activityassay in vitro in NB2 cells culture (FIGS. 3A-3B). It was proved thatthe biological activity of the recombinant hGH produced in the heifer'smilk is within the method's error rank, at the normal values for humannatural hGH. Moreover, the obtained milk was studied by Western blot, inwhich a main band, corresponding to intact hGH, was detected. Additionalminor bands corresponding to cleaved variants and aggregates were alsofound, as expected in these productive systems.

With the information regarding the biological activity and the dailyvolumes, it was possible to calculate the daily production of hGH usingEquation 1, where mhGH is the daily produced mass of hGH in milligrams;BA, the biological activity in International Units; SA, the specificactivity of hGH (3 IU/mg); and V, the daily volume of collected milk.The data is shown in FIG. 4A. A plot of the daily mass of hGH is shownin FIG. 4B. In order to establish a visual correlation between the dailymass of hGH and daily volume of milk, the latter was also plotted inFIG. 4B. $\begin{matrix}{m_{hGH} = \frac{BA}{{SA} \times V}} & \left( {{Eq}.\quad 1} \right)\end{matrix}$

As it can be observed from this information, the daily mass of hGH inmilk and the daily volume of milk tend to augment as the cow develops(the former in a greater proportion, though), which constitutes anupward trend in the recombinant hormone productivity (grams of hGH permilk liter). It can be noticed that this productivity passed from around2 g of hGH per liter (first milking), when the product was colostrum, toan average amount of 5 g hGH per milk liter from the second lactatingmonth forth. Thus, an unexpectedly high yield of human growth hormonewas obtained as productivity increased, in a way more or less continuousas the fluid quality turned from colostrum to milk.

Although at present the mass of hGH produced per day is outstandingindeed, it should be noted that, as the cow is not fully grown yet, theupward trend in mass of recombinant protein produced per day shouldcontinue in the future, until a maximum is reached.

In parallel with the tests performed on milk, a different set of assayswere carried out on the cow's serum, whose results are shown in FIGS.5A-5C. First, measurements of the concentration of hGH in the cow'sserum were performed. The results (FIG. 5A) are plotted in a graphictogether with the daily mass of hGH in milk, to allow a comparison ofboth magnitudes (FIG. 5B).

The reference range for GH in serum (in humans) is 0.06-5 ng/ml.Assuming a hypothetical similar range for bovines, it can be noticedthat, except for the beginning, the whole curve of hGH in the transgeniccow's serum versus date lies well over the upper limit of said range.This fact notwithstanding, it must be taken into account that, althoughhGH and the corresponding bovine hormone (bGH) are very similarregarding their amino acid sequence and 3D-structure, the former,although fully functional, is not fully active in cattle.

Therefore, in order to assess the potential risk to the cow's health dueto these high levels of hGH in its serum, measurements of serumconcentration of IGF-1 (Insulin-like Growth Factor 1, also known asSomatomedin C) were performed in parallel (FIG. 5A). Growth hormoneperforms its functions primarily through IGF-1, which is made in theliver. Because IGF-1 mediates many of the in vivo cell division andmetabolic effects of growth hormone, IGF-1 assessment is a valuablediagnostic tool for the indirect evaluation of suspected growth hormonedisorders. Thus, IGF-1 represents a dependable indicator of bioavailablegrowth hormone. The results of these analyses are shown in FIG. 5C,together with the ones corresponding to hGH, to permit the simultaneousvisualization of both magnitudes.

Moreover, IGF-1 and hGH were measured in the serum of a group ofnon-transgenic cows in order to have a control group and thus toestablish a comparison with the data corresponding to the transgeniccow. The averages of the measurements of both proteins for thenon-transgenic group and the transgenic cow are displayed in Table 3below. TABLE 3 Averages [IGF-1] in Serum [hGH] in serum Non-transgenic123.40 0.28 Transgenic 484.02 656.98

It is worth noticing that the average serum concentration of hGH in thenon-transgenic group lies within the hypothetical reference range,whereas the average for the transgenic cow is well over the upper limitof said range. Besides, it is undoubted that the average level of IGF-1in the transgenic animal's serum is categorically higher than the onecorresponding to non-transgenice cows, which constitutes a findamentaldifference.

Therefore, although the high concentration of hGH in the transgeniccow's serum (which in humans is known to cause disorders with severeconsequences, such as diabetes mellitus, hypertension, increased risk ofcardiovascular disease and enlargement of body organs, including theliver, spleen, kidneys and heart) should render the animal,theoretically, non-viable, this would not be representing, apparently,an obstacle to its health and well being. A cow with alarmingly highlevels of a foreign hormone in its blood, but which is perfectly healthyand yields an outstanding productivity of a recombinant proteinconstitutes an unexpected and innovative contribution.

Another innovative aspect of the present invention is that therecombinant hGH which enters the cow's bloodstream, stimulates themammary gland to produce more milk. This effect is indirectly achieved,i.e., through the action of IGF-1. This molecule increases the bloodflow through the mammary gland, providing critical precursors for thesynthesis of milk fat, protein, and lactose. Thus, IGF-1 acts to directnutrients through the blood to the cells in the udder where they aid inthe production of milk. Therefore, a self-stimulating animal isattained, since the recombinant hGH produced in the milk of thetransgenic cow is promoting a sustained increase in the volume of milkproduced by the animal through the stimulation of its mammary gland,with the corresponding secretion of more hGH in its milk.

EXAMPLE 5 Obtaining Transgenic Calves by Subcloning

Five samples of tissue from the ear of a transgenic calf were takenemploying a 1.5-mm-diameter needle, whose end had been previouslybeveled for this purpose. The samples were shipped under refrigerationto the laboratory in a PBS-based medium containing antibiotics andantimycotics.

Afterwards, the tissue samples were incubated for 72 hours in MEM mediumwith 10% bovine fetal serum and antibiotics at 39° C. and atmosphere of5% CO₂ Eventually, the tissue samples were removed, and fibroblasts atthe periphery of the plate were allowed to grow until confluence. Oncethis had been achieved, the fibroblasts were incubated for at least 5days without changing the culture medium in order to attain theirsynchronization in G₀ stage, which was assessed by means ofvisualization with a microscopy.

After trypsinization, individual fibroblasts were fused with enucleatedbovines oocytes according to Example 2, and embryos thus obtained werecultured in SOF medium and atmosphere of 5% CO₂+5% ) ₂+90% N₂ up to thestage of blastocyst. Afterwards, generally two blastocysts weretransferred non-surgically per recipient cow, and pregnancies weredetermined at 30-35 days by ultrasonography.

The implanted cows are allowed to normally pass the pregnancy up to anatural delivery. Eventually a chirurgic approach (Caesarea) could beused for delivery. The newborns are fed with Ig rich colostrum duringthe first 48 hours, and then synthetic, later natural (all of them freeof animal origin compounds) foods are used.

FIGS. 6A and 6B show measurements of serum concentration of hGH andIGF-1 performed in parallel for two of the transgenic animals obtainedby subcloning of a transgenic cow, and the results of these analyses aredepicted in FIGS. 6C and 6D, respectively, to permit the simultaneousvisualization of both magnitudes for each animal. Since at present thecalves are young, the values for both hGH and IGF-1 still lie within therespective range of reference, but it is expected that they will risethe same way they did in the transgenic cow out of which these twoclones were obtained.

EXAMPLE 6 Obtaining Transgenic Calves by Artificial Insemination of aSuperovulated Transgenic Cow

An alternative approach for obtaining transgenic bovines will bedisclosed in this example. This method comprises superovulating atransgenic cow by means of a hormonal treatment; artificiallyinseminating said cow; recollecting the embryos thus generated; theimplantation of said embryos in surrogate cows; and the development ofthe pregnancy up to the birth of the animals. A description of thisprocedure is presented below.

Superovulation

In the morning of day 1 (i.e., the day the procedure started), 150 μg ofprostaglandins (D(+)-clorprostenol, Arsaprost®, Arsa) were administeredto the transgenic cow by intramuscular route. The animal was subjectedto a 4-kg daily diet containing approximately 15% of proteins (beforeday 1, the animal had been given 2 kg of food, with the same content ofproteins). In the morning of day 8, a CIDR (controlled internal drugrelease) device of progesterone was placed intravaginally. Besides, 50mg of progesterone and estradiol were administered by intramuscularroute. The amount of food the animal was fed rose to 6 kg/day, with thesame content of proteins. Then, two intramuscular injections of FSH andLH (PLUSET®, Calier) were administered on days 12, 13 and 14 (one in themorning and the other in the afternoon). The following day (day 15), thetreatment went on with the administration, by intramuscular route, oftwo injections of PLUSET® (one in the morning and the other in theafternoon) and two injections of 150 μg of prostaglandins each (sameadministration regimen). In the morning of day 16, the CIDR was removed.The total amount of PLUSET® administered throughout the superovulationphase was 350 IU.

Insemination

This phase comprised three successive administrations (the first andsecond, in the morning and in the afternoon of day 17, respectively, andthe last, in the morning of day 18) of semen from a donor jersey bull,which had been obtained previously and kept frozen to preserve theviability of the spermatozoids.

Collection of Embryos and Their Implantation in Surrogate Cows

The collection of embryos by flushing of both horns of the cow's uteruswith 1 l of DMPBS (Nutricell®) took place in the morning of day 26.Immediately afterwards, two embryos were transferred non-surgically perrecipient cow, and pregnancies were determinined at 30-35 days byultrasonography.

The implanted cows are allowed to normally pass the pregnancy up to anatural delivery. Eventually a chirurgic approach (Caesarea) could beused for delivery. The newborns are fed with Ig rich colostrum duringthe first 48 hours, and then synthetic, later natural (all of them freeof animal origin compounds) foods are used.

Since the generation of biological offspring obeys Mendel's law, half ofthe animals being born as a consequence of the procedure described aboveshould be transgenic, and, of these, half should be males and the otherhalf, females. Therefore, there is a high probability of obtaining atransgenic male (founder animal), whose semen could be useful forsetting up a Master Bank of jersey transgenic semen to be used for theinsemination of superovulated transgenic/non-transgenic cows in order toexpand the transgenic herd.

EXAMPLE 7 Purification of Recombinant hGH From Milk

Once verified the approximate molecular weight, the Western blot resultsand the biological activity of the recombinant hGH produced in thecalf's milk are correct, an exhaustive purification process wasperformed, for it is imperative, when manufacturing a biopharmaceuticalproduct, that the protein of interest should be purified to homogeneity,in order to avoid the presence of possible contaminants in said product.This process comprised the steps of: obtaining the skim of the milk bymeans of centrifugation and dilution of the supernatant obtained toachieve a better solubility of recombinant hGH eventually retained inthe micelles of casein (clarification); and passage of this solutionthrough an expanded-bed anionic exchange chromatography column (analternative to this step is the employ of an immunoaffinity column, seeExample 8 below); the resulting solution is subdued to a reverse phaseHPLC (C4) step; fractions rich in recombinant hGH are afterwardssubjected to an anionic interchange chromatography.

Purified material is desalted, concentrated and subjected to molecularexclusion chromatography. This separates by a molecular weight in orderto obtain the pure recombinant hGH.

The procedure for the purification of human growth hormone (hGH) frommilk comprises the following steps in order: (a) clarification (b)expanded-bed anionic exchange chromatography, (c) reverse phasechromatography, (d) anionic exchange chromatography, (e) molecularexclusion chromatography (desalting), (f) concentration and (g)molecular exclusion chromatography.

Clarification

Fresh milk was mixed with a sufficient amount of Tween 80 in order toobtain a 0.5% solution. After addition of Tween 80, 2 M Tris-HCl wasadded to get a pH of 7.3±0.1. Afterwards, the product was homogeneizedfor 30 minutes, and then centrifugated at 14000 g in order to separatethe fat layer. Later, the resulting solution was diluted with 0.5% Tween80 up to a conductivity of less than, or equal to, 1500 μS/cm. The pHwas adjusted to 7.3±0.1 with 2 M Tris-HCl and then the product wasfiltered through a 0.8 μm pore membrane and stored conveniently.

Expanded-Bed Anionic Exchange Chromatography

The material resulting from the previous step is chromatographed usingan anionic exchange matrix according to the following parameters:

-   -   1. Equipment:        -   A. Column:            -   1) Diameter: 5 cm            -   2) Bed height: 30 cm (compacted bed)            -   3) Matrix:                -   a. Streamline Q XL (Amersham)                -   b. Volume: 600 ml    -   2. Solutions and buffers:        -   A. 0.5 N NaOH        -   B. 20% Ethanol        -   C. Buffer A: 20 mM Tris.HCl, pH 7.3        -   D. Buffer B: 500 mM Tris.HCl, pH 7.3        -   E. Buffer C: 20 mM Tris.HCl, 150 mM NaCl, pH 7.3        -   F. Buffer D: 20 mM Tris.HCl, 500 mM NaCl, pH 7.3    -   3. Material to be chromatographed        -   A. Clarified milk.        -   B. Sample conditions:            -   1) Volume: 25±51            -   2) Conductivity: ≦1500 μS/cm            -   3) pH: 7.3±0.1

To equilibrate the column, 1.5 volumes of the column (“vc”) (900 mL) ofpurified water were passed through it, at a flow of 115±5 cm/hour(descending flow). Afterwards, the following solutions or buffers in thequantities hereinafter detailed were sequentially passed through it, atan flow of 230±30 cm/hour (ascending flow): 3.0 vc (1,800 ml) of 0.5 NNaOH; 3.0 vc (1,800 ml) of purified water; 1.0 vc (600 ml) of Buffer B;and, finally, 3.0 vc (1,800 ml) of Buffer A.

Once the column was equilibrated, the material to be chromatographed wasloaded. Said loading was performed at 12±3° C. and at a flow of 230±30cm/hour. Thereafter, the elution was performed at a 115±15 cm/hour flowand at the same temperature. Firstly, a sufficient amount of Buffer Awas passed through the column (ascending flow), and secondly thesolutions and buffers hereinafter detailed were passed in the followingorder (descending flow): 1.5 vc (900 ml) of Buffer A; 2.0 vc (1,200 ml)of Buffer C; and, finally, 2.0 vc (1,200 ml) of Buffer D.

Once the step had finished, the following solutions or buffers in thequantities hereinafter detailed were sequentially passed through thecolumn, in order to clean it: 1.5 vc (900 ml) of purified water; 1.5 vc(900 ml) of 0.5 N NaOH; 2.0 vc (1,200 ml) of purified water; 1.0 vc (600ml) of Buffer B; 1.5 vc (900 ml) of purified water; and, finally, 1.5 vc(900 ml) of 20% Ethanol.

The selected hGH containing fractions were assayed for total proteins(by Bradford method) and for the protein of interest (by RIA), andstored at 2-8° C.

Reverse Phase Chromatography

The material resulting from the previous step is chromatographedaccording to the following parameters:

-   -   1. Equipment:        -   A. Column:            -   1) Diameter: 4 cm            -   2) Bed height: 48 cm            -   3) Matrix                -   a. BakerBond Wide-Pore Butyl (C4) 15 μm prep LC                    Packing (Baker)                -   b. Volume: 600 ml    -   2. Solutions and buffers:        -   A. Mobile Phase 1 (MP1): 30 mM. NaHCO₃, pH 7.2:Purified            water:Acetonitrile (35:55:10)        -   B. Mobile Phase 2 (MP2): 30 mM NaHCO₃, pH 7.2:Purified            water:Acetonitrile (20:10:70)        -   C. 50% Methanol    -   3. Material to be chromatographed        -   A. Pool of selected fractions resulting from the previous            step.        -   B. Sample conditions:            -   1) Volume: 30±15 l            -   2) pH: 7.3±0.3

To equilibrate the column, the following solutions or buffers in thequantities hereinafter detailed were sequentially passed through it, ata flow of less than, or equal to, 478 cm/hour: 0.3 vc (180 ml) of 50%methanol; thereafter, a gradient of 50% methanol-MP2 was appliedstarting from a 100:0 ratio of said solutions until a 0:100 ratio ofsaid solutions in a total volume of 1.0 vc (600 ml) was reached; oncethe gradient was finished, 1.0 vc (600 ml) of MP2 was passed through thecolumn; thereafter, a gradient of MP2-MP1 was applied starting from a100:0 ratio of said solutions until a 0:100 ratio of said solutions in atotal volume of 1.0 vc (600 ml) was reached; and, finally, 2.0 vc (1,200ml) of MP1 were passed through the column.

Once the column was equilibrated, the material to be chromatographed wasfiltered through a 0.45 μm pore membrane, and loaded immediatelyafterwards. Said loading was performed at 20±5° C. and at a flow of lessthan, or equal to, 238 cm/hour. Thereafter, the elution was performed ata 478±78 cm/hour flow and at the same temperature, and the solutions andbuffers hereinafter detailed were passed in the following order: 1.0 vc(600 ml) of MP1; a gradient of MP1-MP2, starting from a 65:35 ratio ofsaid solutions until a 45:55 ratio of said solutions in a total volumeof 18.0 vc (9,000 ml) was reached; 1.0 vc (600 ml) of MP1-MP2 in a 45:55ratio; and, finally, 2.0 vc (1,200 ml) of MP2.

Once the step had finished, in order to clean the column, a gradient ofMP2-50% Methanol was applied, starting from a 100:0 ratio of saidsolutions until a 0:100 ratio of said solutions in a total volume of 1.0vc (600 ml) was reached; and, finally, 2.0 vc (1,200 ml) of 50% methanolwere passed through the column.

The fractions resulting from this chromatography were assayed bySDS-PAGE homogeneous 20% and for the oxidized hGH, and, depending on theresults, a selection was performed. Afterwards, the selected hGHcontaining fractions were assayed for total proteins (by Bradfordmethod), and stored at 2-8° C.

Anionic Exchange Chromatography

The material resulting from the previous step is chromatographed usingan anionic exchange matrix, as follows:

-   -   1. Equipment:        -   A. Column:    -   1) Diameter: 5 cm    -   2) Bed height: 25 cm    -   3) Matrix        -   -   -   a. Source 30Q (Pharmacia)                -   b. Volume: 500 ml    -   2. Solutions and buffers:        -   A. 20% Ethanol        -   B. Solution K: 0.5 N NaOH, 3M NaCl        -   C. Solution L: 50 mM Tris, pH 7.50        -   D. Solution M: 0.1 N HCl, 3 M NaCl        -   E. Mobile Phase 3 (MP3): Solution L:Acetonitrile (70:30)        -   F. Mobile Phase 4 (MP4): 50 mM Tris, 0.1 M NaCl, pH            7.50:Acetonitrile (70:30)    -   3. Material to be chromatographed        -   A. Selected fractions resulting from the previous step.        -   B. Sample conditions:            -   1) Volume: 4.5±1 l            -   2) pH: 7.2±0.2

To equilibrate and sanitize the column, the following solutions orbuffers in the quantities hereinafter detailed were sequentially passedthrough it, at a flow of less than, or equal to, 183±20 cm/hour: 1.0 vc(500 ml) of purified water; 1.0 vc (500 ml) of Solution K; 1.0 vc (500ml) of Solution L; and, finally, 1.0 vc (500 mL) of MP3.

Once the column was equilibrated, the material to be chromatographedloaded. Said loading was performed at 20±5° C. and at a flow of lessthan, or equal to, 183 cm/hour. Thereafter, the elution was performed ata 183±20 cm/hour flow and at the same temperature, and the solutions andbuffers hereinafter detailed were passed in the following order: 1.0 vc(500 ml) of MP3; a gradient of MP3-MP4, starting from a 15:85 ratio ofsaid solutions until a 25:75 ratio of said solutions in a total volumeof 5.0 vc (2500 ml) was reached; and, finally, 2.0 vc (1000 ml) of MP4was passed through the column.

Once the step had finished, the following solutions or buffers in thequantities hereinafter detailed were sequentially passed through thecolumn, in order to clean it: a gradient of MP4-purified water, startingfrom a 100:0 ratio of said solutions until a 0:100 ratio of saidsolutions in a total volume of 0.5 vc (250 ml) was reached; 0.5 vc (250ml) of purified water; a gradient of purified water-Solution K, startingfrom a 100:0 ratio of said solutions until a 0:100 ratio of saidsolutions in a total volume of 0.5 vc (250 ml) was reached; 1.0 vc (500ml) of Solution K; a gradient of Solution K-purified water, startingfrom a 100:0 ratio of said solutions until a 0:100 ratio of saidsolutions in a total volume of 0.5 vc (250 ml) was reached; 0.5 vc (250ml) of purified water; a gradient of purified water-Solution M, startingfrom a 100:0 ratio of said solutions until a 0:100 ratio of saidsolutions in a total volume of 0.5 vc (250 ml) was reached; 1.0 vc (500ml) of Solution M; a gradient of Solution M-purified water, startingfrom a 100:0 ratio of said solutions until a 0:100 ratio of saidsolutions in a total volume of 0.5 vc (250 ml) was reached; 1.0 vc (500ml) of purified water; a gradient of purified water-Solution L, startingfrom a 100:0 ratio of said solutions until a 0:100 ratio of saidsolutions in a total volume of 0.5 vc (250 ml) was reached; 0.5 vc (250ml); 0.5 vc (250 ml) of Solution L; a gradient of Solution L-purifiedwater, starting from a 100:0 ratio of said solutions until a 0:100 ratioof said solutions in a total volume of 0.5 vc (250 ml) was reached; and,finally, 1.5 vc (750 ml) of purified water.

The selected hGH containing fractions were assayed for total proteins(by Bradford method), and stored at 2-8° C.

Molecular Exclusion Chromatography

The material resulting from the previous step is chromatographed using amolecular exclusion matrix, as follows:

-   -   1. Equipment:        -   A. Column:            -   1) Diameter: 5 cm            -   2) Bed height: 25 cm            -   3) Matrix                -   a. Cellufine GH25 (Millipore)                -   b. Volume: 500 ml    -   2. Solutions and buffers:        -   A. 0.5 N NaOH        -   B. 20% Ethanol        -   C. Buffer C: 150 mM NaH₂PO₄, pH 7.2        -   D. Buffer G: 320 mM Glycine, 10 mM NaH₂PO₄, 0.1% Tween 80,            pH 6.9    -   3. Material to be chromatographed        -   A. Selected fractions resulting from the previous step.        -   B. Sample conditions:            -   1) Volume:0.5±0.2 l            -   2) pH: 7.5±0.5

To equilibrate and sanitize the column, the following solutions orbuffers in the quantities hereinafter detailed were sequentially passedthrough it, at a flow of less than, or equal to, 180 cm/hour: 1.0 vc(500 ml) of purified water; 1.0 vc (500 ml) of 0.5 N NaOH; 0.5 vc (250ml) of purified water; 0.5 vc (250 ml) of Buffer C; and, finally, 2.0 vc(1000 ml) of Buffer G.

Once the column was equilibrated, the material to be chromatographed wasloaded. Said loading was performed at 20±5° C. and at a flow of 183±20cm/hour. Thereafter, the elution was performed at the same flow rate andtemperature, and 1.0 vc (500 ml) of Buffer G was passed through thecolumn, as many times as the number of runs which was necessary toperform.

Once the step had finished, the following solutions or buffers in thequantities hereinafter detailed were sequentially passed through thecolumn, in order to clean it: 0.5 vc (250 ml) of purified water; 1.0 vc(500 ml) of 0.5 N NaOH; 0.5 vc (250 ml) of purified water; 0.5 vc (250ml) of Buffer C; 0.5 vc (250 ml) of purified water; and, finally, 1.5 vc(750 ml) of 20% ethanol.

The selected hGH containing fractions were assayed for total proteins,and stored at 2-8° C.

Concentration

The fractions resulting from the previous example were concentratedaccording to the conditions described below:

-   -   1. Equipment:        -   A. Peristaltic pump: Watson Marlow—Cat. No. 302S        -   B. Tubing: Watson Marlow-Cat. No. 902.0080.016        -   C. Concentrator: Prep Scale Millipore—Cat. No. CDU F006LC    -   2. Solutions and buffers:        -   A. 0.28% Sodium Dodecyl Sulfate (SDS)        -   B. 0.06% Triton        -   C. 0.125 N NaOH        -   D. Buffer G: 320 mM Glycine, 10 mM NaH₂PO₄, 0.1% Tween 80,            pH 6.9    -   3. Material to be processed:        -   A. Selected fractions resulting from the previous example.        -   B. Sample conditions:            -   1) Volume: 1.0±0.5 l            -   2) Conductivity: 1200±100 μS/cm            -   3) pH: 6.9±0.1

The equipment was first cleaned, sanitized and equilibrated, and thefollowing sequence of solutions and buffers were flowed through theequipment: 2 l of 0.125 N NaOH; 10 l of purified water; and, finally, 2l of Buffer G. The equipment was then ready to be used for concentrationon the selected fractions, following the usual methodology. Theconcentration procedure was performed until a protein concentration of15 mg/ml (assessed by Bradford method) was reached.

The selected fractions were filtered through a 0.22 μm pore membrane,assayed for total proteins (by Bradford method), and stored at 4° C.

The conductivity and the pH of the selected fractions were 1,100-1,300μS/cm and 6.9±0.1, respectively.

Molecular Exclusion Chromatography

The material resulting from the previous step is chromatographed using amolecular exclusion matrix, as follows:

-   -   1. Equipment:        -   A. Column:            -   1) Diameter: 5 cm            -   2) Bed height: 92 cm            -   3) Matrix                -   a. Sephacryl S-200 High Resolution (Amersham                    Pharmacia)                -   b. Volume: 1,800 ml    -   2. Solutions and buffers:        -   A. 0.5 N NaOH        -   B. 20% Ethanol        -   C. Buffer H: 320 mM Glycine, 2.2 mM NaH₂PO₄, 1.8 mM Na₂HPO₄,            pH 7.30    -   3. Material to be chromatographed        -   A. Fractions selected from the previous step, concentrated        -   B. Sample conditions:            -   1) Volume: 40±20 ml            -   2) Conductivity: 1,200±100 μS/cm            -   3) pH: 7.3±0.1

To equilibrate and sanitize the column, the following solutions orbuffers in the quantities hereinafter detailed were sequentially passedthrough it, at a flow of less than 46 cm/hour: 1.0 vc (1,800 ml) ofpurified water; 1.0 vc (1,800 ml) of 0.5 N NaOH; and, finally, 2.0 vc(3,600 ml) of Buffer H.

Once the column was equilibrated, the material to be chromatographed wasloaded. Said loading was performed at 20±5° C. and at a flow of 46±15cm/hour. Thereafter, the elution was performed at the same flow rate andtemperature, and 1.0 vc (1,800 ml) of Buffer H was passed through thecolumn, as many times as the number of runs which was necessary toperform.

Once the step had finished, the following solutions or buffers in thequantities hereinafter detailed were sequentially passed through thecolumn, in order to clean it: 1.0 vc (1,800 ml) of purified water; and1.5 vc (2,700 ml) of 20% ethanol.

The fractions containing pure hGH were aseptically filtered through a0.22 μm pore membrane into sterile, depyrogenated plastic bottles,assayed for total proteins, and stored at −20° C.

EXAMPLE 8 Alternative Procedure for the Purification of hGH From Milk

Instead of the purification method previously described, an alternativescheme can be employed in order to purify the recombinant hGH containedin the milk. The main difference between the procedure described inExample 7 and the alternative one presented in this example is that thesecond step of the former involves expanded-bed anionic exchangechromatography, whereas the corresponding step of the latter entailsimmunoaffinity chromatography. The clarification steps of bothprocedures are also slightly different. Since the rest of bothpurification schemes are identical, only the first two steps of thealternative procedure will be described below.

Clarification

Fresh milk was mixed with a sufficient amount of Tween 80 in order toobtain a 0.5% solution. After addition of Tween 80, 1 M Tris was addedto get a pH of 7.3±0.3. Afterwards, the product was homogeneized for 30minutes, and then centrifugated at 14000 g in order to separate the fatlayer. Later, the resulting solution was diluted 20-fold with Buffer S(50 mM Tris.HCl, 500 mM NaCl, 0.5% Tween 80, pH 7.3), and then filteredthrough a 0.45 μm pore membrane and stored conveniently.

Immunoaffinity Chromatography

The material resulting from the previous step is chromatographed usingan immunoaffinity interaction matrix (Affigel 10 Ester Agarose,manufactured by BioRad, with covalently attached anti-GH MonoclonalAntibodies, manufactured by Bio Sidus) according to the followingparameters:

-   -   1. Equipment:        -   A. Column:            -   1) Diameter: 30 cm            -   2) Bed height: 15 cm            -   3) Matrix:            -   a. Affigel 10 Ester Agarose (BioRad), with covalently                attached anti-GH Monoclonal Antibodies (Bio Sidus)                -   b. Volume: 10 l    -   2. Solutions and buffers:        -   A. Buffer A: 50 mM Tris.HCl, 500 mM NaCl, pH 7.2        -   B. Buffer B: 100 mM Citric Acid, pH 3.0        -   C. Buffer C: 150 mM NaH₂PO₄, pH 7.2        -   D. Buffer D: 50 mM Tris.HCl, 500 mM NaCl, 500 mM            Guanidine.HCl, pH 7.2        -   E. Buffer E: 50 mM Tris.HCl, 500 mM NaCl, pH 7.2, 0.2%            Sodium Azide, 0.1 g/l Gentamicine.    -   3. Material to be chromatographed        -   A. Clarified milk.        -   B. Sample conditions:            -   1) Volume: 30-50 l            -   2) Conductivity: 45±15 mS/cm            -   3) pH: 7.3±0.3

To equilibrate and sanitize the column, if it had not been used in thelast seven days, the following solutions or buffers in the quantitieshereinafter detailed were sequentially passed through it, at a flow ofless than 51 cm/hour: 1.0 volume of the column (“vc”) (10 l) of BufferA; 2.0 vc (20 l) of Buffer D; 2.0 vc (20 l) of Buffer A; 1.0 vc (10 l)of Buffer B; 2.0 vc (20 l) of Buffer C; and, finally, 1.0 vc (10 l) ofBuffer A.

On the other hand, if the column had been used in the last seven days,the following solutions or buffers in the quantities hereinafterdetailed were sequentially passed through it, at a flow of less than 51cm/hour: 1.0 vc (10 l) of Buffer C; and, finally, 2.0 vc (20 l) ofBuffer A.

Once the column was equilibrated, the material to be chromatographed wasloaded. Said loading was performed at 5±3° C. and at a flow of less than51 cm/hour. Thereafter, the elution was performed at a 42±9 cm/hour flowand at the same temperature, and the solutions and buffers hereinafterdetailed were passed in the following order: 2.0 vc (20 l) of Buffer A;and 1.5 vc (15 l) of Buffer B.

Once the step had finished, the following solutions or buffers in thequantities hereinafter detailed were sequentially passed through thecolumn, in order to clean it: 2.0 vc (20 l) of Buffer D; 2.0 vc (20 l)of Buffer A; and, finally, 2.0 vc (20 l) of Buffer E.

The selected hGH containing fractions were assayed for total proteins(by Bradford method) and for the protein of interest (by RIA), andstored at 4° C.

EXAMPLE 9 Quality Control of Pure Recombinant hGH

Two batches of pure recombinant hGH were subjected to a series of assaysto verify that the product is indistinguishable from natural hGH. Suchprocedures included, but are not limited to, SDS/PAGE, Western blot,biological activity in vitro (cells nb2) and in vivo (hypophysectomizedrats), peptide mapping, determination of the complete aminoacidsequence, isoelectric focusing (IEF), and reverse-phase and sizeexclusion HPLC analyses. The results obtained in all those assays wereexactly the same for both recombinant and natural hGH, which proves thatthe pure recombinant hGH corresponds exactly to the natural hGH, beingthus suitable for manufacturing a biopharmaceutical product.

Having now fully described the invention, it will be understood by thoseof ordinary skill in the art that the same can be performed within awide and equivalent range of conditions, formulations and otherparameters without affecting the scope of the invention or anyembodiment thereof. All patents and publications cited herein are fullyincorporated by reference herein in their entirety.

1. A method of producing a protein comprising: a) making a non-humantransgenic mammal that produces a protein of interest in its milk; b)obtaining said milk from said non-human transgenic mammal; and c)purifying said protein of interest from said milk.
 2. The methodaccording to claim 1, wherein said non-human transgenic mammal is madeby a process comprising: a) obtaining a gene which encodes a protein ofinterest; b) cloning said gene into a plasmid whereby said gene isoperably linked to a promoter that will direct the expression of saidgene in mammary cells, resulting in an expression plasmid; c)transfecting somatic cells with said expression plasmid so that saidplasmid is incorporated into the genome of said somatic cells, resultingin transgenic somatic cells; d) enucleating a mature oocyte, resultingin an enucleated oocyte; e) fusing one of said transgenic somatic cellswith said enucleated oocyte resulting in a monocell embryo; f)implanting said embryo in the uterus of a receptive mammal; and g)monitoring the pregnancy through the birth of the transgenic mammal. 3.The method of claim 2, wherein said promoter is a beta casein promoter,and wherein said protein of interest is human growth hormone.
 4. Themethod of claim 3, wherein the expression plasmid is pRβhGH.
 5. Themethod of claim 4, wherein said expression plasmid further comprises aneomycin resistance gene.
 6. The method of claim 5, wherein saidexpression plasmid is pRNeo.
 7. The method of claim 2, wherein saidmammal is a bovine that produces recombinant human growth hormone in itsmilk, whose genome comprises an integrated plasmid, wherein said plasmidcomprises the human growth hormone gene and a beta casein promoter thatdirects expression of said gene in mammary cells of said mammal.
 8. Themethod of claim 7, wherein said plasmid is pRβhGH.
 9. The method ofclaim 8, wherein said plasmid further comprises a neomycin resistancegene.
 10. The method of claim 9, wherein said plasmid is pRNeo.
 11. Themethod of claim 2, wherein said somatic cells are fibroblasts.
 12. Themethod of claim 2, wherein said transgenic somatic cells are obtained byisolation from a female transgenic for the production of said protein ofinterest in its milk.
 13. The method of claim 12, wherein saidtransgenic somatic cells are fibroblasts.
 14. The method according toclaim 1, wherein said non-human transgenic mammal is made by a processcomprising: a) superovulating a female non-human mammal which istransgenic for the production of said protein of interest in its milk;b) artificially inseminating said mammal with semen obtained from a malenon-human, non-transgenic mammal, to produce embryos; c) collecting saidembryos; d) implanting said embryos in the uterus of a receptive mammal;and e) monitoring the pregnancy through the birth of the transgenicmammal.
 15. The method according to claim 1, wherein said non-humantransgenic mammal is made by a process comprising: a) superovulating afemale non-human mammal which is transgenic for the production of saidprotein of interest in its milk; b) artificially inseminating saidmammal with semen obtained from a male non-human mammal which istransgenic for the production of said protein of interest, to produceembryos; c) collecting said embryos; d) implanting said embryos in theuterus of a receptive mammal; and e) monitoring the pregnancy throughthe birth of the transgenic mammal.
 16. The method according to claim 1,wherein said non-human transgenic mammal is made by a processcomprising: a) superovulating a female non-human, non-transgenic mammal;b) artificially inseminating said mammal with semen obtained from a malenon-human mammal which is transgenic for the production of said proteinof interest, to produce embryos; c) collecting said embryos; d)implanting said embryos in the uterus of a receptive mammal; and e)monitoring the pregnancy through the birth of the transgenic mammal. 17.The method of claim 2, wherein said mammal is of bovine species, porcinespecies, ovine species, caprine species or rodent species.
 18. Themethod of claim 17, wherein said mammal is of bovine species.
 19. Themethod of claim 2, wherein said protein of interest is a mammaliangrowth hormone.
 20. The method of claim 19, wherein said mammaliangrowth hormone is human growth hormone, bovine growth hormone, porcinegrowth hormone, ovine growth hormone, caprine growth hormone or rodentgrowth hormone.
 21. The method of claim 20, wherein said mammaliangrowth hormone is human growth hormone.
 22. The method of claim 21,wherein said mammal produces human growth hormone at a level of greaterthan about 1.0 g hGH/L milk.
 23. The method of claim 22, wherein saidmammal produces human growth hormone at a level of greater than about2.0 g hGH/L milk.
 24. The method of claim 23, wherein said mammalproduces human growth hormone at a level of greater than about 3.0 ghGH/L milk.
 25. The method of claim 24, wherein said mammal produceshuman growth hormone at a level of greater than about 4.0 g hGH/L milk.26. The method of claim 25, wherein said mammal produces human growthhormone at a level of greater than about 5.0 g hGH/L milk.
 27. Themethod of claim 26, wherein said mammal produces human growth hormone ata level of greater than about 6.0 g hGH/L milk.
 28. The method of claim19, wherein production of said mammalian growth hormone by said mammalstimulates said mammal to produce more milk comprising said mammaliangrowth hormone.
 29. The method of claim 2, wherein the gene encodingsaid protein of interest (linked to a promoter that directs theexpression of said gene in mammary cells) is found in somatic cells andgerm cells of said mammal.
 30. A method of purifying a recombinantgrowth hormone from milk of a non-human transgenic mammal that producesa recombinant growth hormone comprising: a) clarifying the milk of anon-human transgenic mammal, resulting in a clarified milk; and b)subjecting said clarified milk to chromatography, resulting in purifiedrecombinant growth hormone.
 31. The method of claim 30, wherein saidchromatography is ion exchange chromatography, reverse phasechromatography, molecular exclusion chromatography or affinitychromatography.
 32. The method of claim 31, wherein multiplechromatography steps are performed.
 33. The method of claim 31, whereinsaid ion exchange chromatography is anion exchange chromatography. 34.The method of claim 31, wherein the affinity chromatography isimmunochromatography.
 35. The method of claim 31, further comprising aconcentration step.
 36. A method of purifying a recombinant growthhormone from milk of a non-human transgenic mammal that produces arecombinant growth hormone comprising: a) clarifying the milk of anon-human transgenic mammal, resulting in a clarified milk; b)subjecting said clarified milk to expanded-bed anion exchangechromatography, resulting in an anion exchange chromatographed material;c) subjecting said anion exchange chromatographed material to reversephase chromatography, resulting in a reverse phase chromatographedmaterial; d) subjecting said reverse phase chromatographed material toanion exchange chromatography, resulting in an anion exchangechromatographed material; e) subjecting said anionic exchangechromatographed material to molecular exclusion chromatography,resulting in a molecular exclusion chromatographed material; f)concentrating said molecular exclusion chromatographed material,resulting in a concentrated material; and g) subjecting saidconcentrated material to molecular exclusion chromatography, resultingin pure recombinant growth hormone.
 37. A method of purifying arecombinant growth hormone from milk of a non-human transgenic mammalthat produces a recombinant growth hormone comprising: a) clarifyingmilk obtained from a transgenic mammal, resulting clarified milk; b)subjecting said clarified milk to immunoaffinity chromatography,resulting in an immunoaffinity chromatographed material; c) subjectingsaid immunoaffinity chromatographed material reverse phasechromatography, resulting in a reverse phase chromatographed material;d) subjecting said reverse phase chromatographed material to anionicexchange chromatography, resulting in an anionic exchangechromatographed material; e) subjecting said anionic exchangechromatographed material to molecular exclusion chromatography,resulting in a molecular exclusion chromatographed material; f)subjecting said molecular exclusion chromatographed material toconcentration, resulting in a concentrated material; and g) subjectingsaid concentrated material to molecular exclusion chromatography,resulting in pure recombinant growth hormone.
 38. The method of claim 36or wherein said growth hormone is a mammalian growth hormone.
 39. Themethod of claim 38, wherein said mammalian growth hormone is humangrowth hormone, bovine growth hormone, porcine growth hormone, ovinegrowth hormone, caprine growth hormone or rodent growth hormone.
 40. Themethod of claim 39, wherein said mammalian growth hormone is humangrowth hormone.
 41. The method of claim 40, wherein said mammal produceshuman growth hormone at a level of greater than about 1.0 g hGH/L milk.42. The method of claim 41, wherein said mammal produces human growthhormone at a level of greater than about 2.0 g hGH/L milk.
 43. Themethod of claim 42, wherein said mammal produces human growth hormone ata level of greater than about 3.0 g hGH/L milk.
 44. The method of claim43, wherein said mammal produces human growth hormone at a level ofgreater than about 4.0 g hGH/L milk.
 45. The method of claim 44, whereinsaid mammal produces human growth hormone at a level of greater thanabout 5.0 g hGH/L milk.
 46. The method of claim 45, wherein said mammalproduces human growth hormone at a level of greater than about 6.0 ghGH/L milk.
 47. The method of claim 36, wherein said non-humantransgenic mammal is of bovine species.
 48. The method of claim 36,wherein said non-human transgenic mammal is a pig, sheep, goat orrodent.